Referring to art FIG. 1, a known dimensioning system 10 includes a conveyor system 12 that moves items along a path of travel, and a component system 14 adjacent to the conveyor system that tracks packages being moved by the conveyor system. Conveyor system 12 includes a number of rollers 16, a belt 24, a bed 18 and a tachometer 20. It should be understood that the conveyor can move the items through the path of travel by means other than belts, for example by driven rollers. Rollers 16 are motor-driven rollers that move conveyor belt 24 in a direction denoted by arrows 26 over bed 18, which provides support to the belt. For purposes of the present discussion, the direction corresponding to the start of conveyor system 12 is referred to as “upstream,” whereas the direction in which conveyor belt 24 moves is referred to as “downstream.”
Tachometer 20 is beneath and in contact with the surface of conveyor belt 24 and rotates with the belt as the belt moves in the direction of arrows 26. As tachometer 20 rotates, it outputs a signal comprising of a series of pulses corresponding to the conveyor belt's linear movement and speed. Tachometer 20, and other devices that provide signals corresponding to the rate of movement of a conveyor belt, from which the locations of items moving in a path of travel along the belt can be determined, should be understood by those of ordinary skill in the art. In general, the number of pulses output by tachometer 20 corresponds to the linear distance traveled by the belt, while pulse frequency corresponds to the belt's speed. The number of tachometer pulses per unit of measurement defines the resolution of the tachometer and its ability to precisely measure the distance that the conveyor belt has moved. Tachometer 20 may be replaced by a shaft encoder, particularly where less accurate measurements are needed.
Component system 14 includes a dimensioner 28, a plurality of barcode scanners 32, and a computer 36, all of which are attached to a frame 38. Frame 38 supports dimensioner 28 and at least one barcode scanner 32 horizontally above conveyor belt 24 so that beams of light emitted by the dimensioner and scanners intersect the top surfaces of packages moved by the belt. Frame 38 also supports additional scanners 32 vertically adjacent to conveyor belt 24 so that beams of light emitted by these scanners intersect the side, back, front or bottom surfaces of packages moved by the belt. One example of prior art scanners include QUAD X laser barcode scanners manufactured by Accu-Sort Systems, Inc. of Telford, Pa., although it should be understood that cameras or other suitable barcode readers could be used, depending on the needs of a given system.
As should be understood in this art, dimensioner 28 detects one or more dimensions of an item on a conveyor. The dimensioner is disposed along the conveyor at a known position relative to the bar code readers. When a package moving along the conveyor reaches the dimensioner, the dimensioner processor opens a package record, determines height, width and length, associates that data in the package record, and outputs the dimension data to the system processor in association with tachometer data that corresponds to the package's location at the dimensioner. Upon receiving the dimensioner data, the system processor opens a package record and associates with the package record the dimension and tachometer data received from the dimensioner.
The system processor also sets an open read window variable and a close read window variable for the barcode scanner. The open read window variable for the barcode scanner is equal to the tachometer value for the downstream-most point on the package, plus a known distance (in tachometer pulses) between the dimensioner and a predetermined position in the path of travel with respect to the barcode scanner. The close read window variable for the barcode scanner is equal to the tachometer value for the upstream-most point on the package, plus a known distance (in tachometer pulses) between the dimensioner and the predetermined position with respect to the barcode scanner.
As should be understood in this art, barcode reader 32 may comprise a laser scanner that projects a plurality of laser lines on the belt, for example in a series of “X” patterns. The scanner outputs a signal that includes barcode information reflected back from the laser lines and a barcode count, which indicates the position in the X patterns at which given barcode information was seen. Thus, the barcode count provides the lateral position on the belt, and the longitudinal position with respect to the centerline of the X patterns, corresponding to the barcode information. The barcode scanner assembly has a photodetector disposed along the conveyor immediately upstream from the X patterns. A processor at barcode scanner assembly 32 monitors the photodetector's output signal and thereby determines when the package's front and back edges pass the photodetector. The barcode scanner also receives the tachometer output. By associating the passage of the package's front and back edges by the photodetector with the tachometer data, the barcode scanner processor determines when the package passes through the X patterns. The barcode scanner processor accordingly determines when valid barcode data may be acquired for the package and acquires the barcode data during that period.
The barcode processor accumulates barcode data while a given package passes through the X patterns and transmits the accumulated barcode data to the system processor when the package reaches a predetermined point in the path of travel following the barcode scanner. More specifically, the barcode scanner processor knows when the front edge of the package passes by the barcode scanner photodetector. After acquiring the package's barcode data over a period based on the package's length, the barcode scanner processor holds the barcode data until a tachometer value the barcode scanner processor associates with the barcode data accumulates to a point indicating that the front edge of the package is at the predetermined point downstream of the scanner. The predetermined point is defined so that the longest package the system is expected to handle can clear the scanner's X patterns. The barcode scanner processor then outputs the barcode data to the system processor.
The system processor relies on tachometer pulses to correctly associate barcode data with a package record. The system processor determines the accumulated tachometer value at the time the barcode data is received from the barcode scanner processor. The open read window and close read window barcode variables for each package structure correspond to the distance between the dimensioner and the predetermined point downstream from the barcode scanner. Thus, the system processor compares the tachometer value associated with the received barcode data with the open read window and close read window barcode variables for the open package structures it maintains in memory. If the tachometer value is between the open read window barcode variable and close read window barcode variable for any open package structure, the system processor assigns the barcode data to that package record. If the tachometer value does not fall within the open window and close window barcode variables stored for any open package record, the barcode data is not assigned to a package record.
The described system of FIG. 1 was directed to barcode scanners that project an X-pattern across the belt. It should be understood to those skilled in the art that X-pattern scanners can be replaced with line scan cameras for detecting and reading barcodes. Line scan cameras like barcode scanners are bulky and heavy and require more than one technician to install and calibrate the scanner in scanning tunnel.
To initially set up and calibrate system 10, the camera tunnel frame is set up and the barcode cameras are mounted to the frame so that they are positioned and orientated properly with respect to the conveyor belt. This requires several technicians to lift the cameras into place in the tunnel and secure them to the frame. In general, prior art cameras are unitary structures that are bulky and cumbersome for a single technician to lift and secure. Moreover, because the cameras operate with high power, a large amount of heat must be expelled from the camera housing so as not to damage the camera electronics and optics. Thus, fans are enclosed in the camera housing to pull air through the housing to cool off the internal components.
Once installed, the cameras require time consuming set-up and calibration techniques and, if removed, the camera setup and calibration must be repeated. Technicians connect each camera to a computer to individually calibrate and set the camera's operating parameters. The technician inputs camera information directly into the camera processor via the computer and may save certain camera settings to a dongle or other portable storage device. Calibration data may include the angle of orientation of the camera, the height of the camera and the location of the camera with respect to the belt and the dimensioner. Once each camera is calibrated and set-up in the tunnel, the cameras are connected to a central computer that receives information captured and processed by each camera. However, should a camera break or need to be serviced, a full calibration and set-up is necessary for the camera being replaced and possibly for the overall tunnel to ensure that all components of the tunnel are properly aligned.
In the system shown in FIG. 1, dimensioner 28 is a triangulation type dimensioner similar to those disclosed in U.S. Pat. Nos. 6,775,012, 6,177,999, 5,969,823, and 5,661,561, the entire disclosures of which are incorporated by reference herein. With regard to these embodiments, dimensioner 28 comprises a light source, such as a laser and a rotating reflector disposed within the dimensioner housing that produce a scanning beam (denoted in phantom at 40) that is directed down at conveyor belt 24. That is, the rotating reflector scans the single point light source across the width of belt 24. Each angular position of the reflector represents an x-axis location across the belt. Scanning beam 40 intersects belt 24 at line 42 in a manner that is transverse (x-axis 80) to the belt's linear movement (y-axis 82) in the path of travel at a fixed angle with respect to an axis normal (z-axis 84) to the belt's surface. Packages moving on belt 24, such as package 62, intersect scanning beam 40, thereby creating an offset in the scanning beam in the y-direction (along y-axis 82). In particular, the laser light source is positioned downstream in the y-axis 82 direction so that the plane of light is reflected at an angle from z-axis 84. Thus, as a box moves downstream the intersection of the plane of light is a continuous line across the belt in along x-axis 80. When a box intersects the plane of light, the portion of the plane intersected by the box will shift forward toward the light source since the light on the box travels a shorter distance than the light that intersects the belt on the left and right sides of the box. This offset or shift in the light on the box surface is proportional to the height of the box.
Both conveyor belt 24 and the packages thereon reflect light created by the scanning beam back to the rotating mirror, which reflects light to a linear array of line scan CCD detectors or a CMOS imager (not shown) within dimensioner 28. The array is oriented parallel to y-axis 82. Because the rotating mirror reflects both the outgoing and reflected laser light, the mirror returns the reflected light to a constant x-axis position, but the reflected light shifts in the y-direction correspondingly to the shift in line 42 caused by the height of a package 62 and the angle at which the scanned laser beam intersects the belt. Thus, the linear array of CCD or CMOS detectors must be accurately aligned in the y-direction to thereby detect the return light's y-axis shift. Moreover, because the array is made up of a single line of pixel sensors, the alignment is critical to detect the reflected light. If the axis of the linear sensor is misaligned with the fixed x-axis point where the mirror directs the reflected light, the sensor will not detect the change in height. The rotating mirror's angular position corresponds to the x-axis position of any given point of reflected light.
Dimensioner 28 generates a signal representative of the height of an object such as package 62 across conveyor belt 24 as described by the y-axis offset detected in scanning beam 40. The signal is also representative of the x-axis positions of the height data by association of that data with the mirror's angular position. Based on the height data and corresponding x-axis data, the dimensioner processor (not shown) determines the cross sectional height profile an object on the belt and, by accumulating such profiles along the object's length, the object's three dimensional profile.
As with the camera, technicians must lift and hold the dimensioner in place while it is secured to the tunnel frame. Next, levels are used to ensure that the dimensioner's detector is parallel to the face of the conveyor belt. If the dimensioner's detector array is out of a substantially parallel adjustment with respect to the belt, the dimensioner may obtain inaccurate dimensions of the object. Additionally, as previously described, should the line scan array not align properly with the rotating mirror, e.g. because of slight misalignments between the array and the rotating mirror, the dimensioner may not detect any shift in the light. Moreover, the rotating mirror may become misaligned during shipping or installation through jarring of the dimensioner.